K. Kobayashi et al. / Tetrahedron 65 (2009) 9633–9636
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3.2.1.4. 4-Methoxyphenyl 2-methylsulfanylmethylsulfanylphenyl
crude 4a was dissolved in THF (5 mL) containing pyridine (0.58 g,
7.3 mmol). To this solution at 0 ꢀC was added SOCl2 (0.17 g,
1.5 mmol) under stirring, and the stirring was continued for 30 min.
Water (15 mL) was added, and the mixture was extracted with Et2O
twice (10 mL each). The combined extracts were washed succes-
sively with saturated aqueous NaHCO3, 1% hydrochloric acid, and
brine, and then dried over anhydrous Na2SO4. Evaporation of the
solvent gave a residue, which was purified by preparative TLC on
silica gel (hexane) to give 5a (0.12 g, 63%); a pale-yellow oil; Rf 0.57
(hexane). The spectral (IR, 1H NMR, and 13C NMR) data for this
compound were identical to those reported previously.4c
ketone (2h). A yellow oil; Rf 0.22 (1:1 Et2O–hexane); IR (neat)
1659 cmꢁ1 1H NMR (400 MHz)
; d 2.08 (s, 3H), 3.87 (s, 3H), 3.92 (s,
2H), 6.92 (d, J¼8.8 Hz, 2H), 7.33–7.47 (m, 3H), 7.61 (d, J¼7.7 Hz, 1H),
7.78 (d, J¼8.8 Hz, 2H). Anal. Calcd C16H16O2S2: C, 63.13; H, 5.30.
Found: C, 63.17; H, 5.51.
3.2.1.5. 4-Methoxyphenyl 2-phenylsulfanylmethylsulfanylphenyl ke-
tone (2i). A yellow oil; Rf 0.29 (1:2 Et2O–hexane); IR (neat)
1653 cmꢁ1 1H NMR (400 MHz)
; d 3.86 (s, 3H), 4.27 (s, 2H), 6.90
(d, J¼8.8 Hz, 2H), 7.19–7.26 (m, 3H), 7.31–7.46 (m, 5H), 7.61
(d, J¼7.7 Hz, 1H), 7.75 (d, J¼8.8 Hz, 2H). Anal. Calcd C21H18O2S2:
C, 68.82; H, 4.95. Found: C, 68.52; H, 5.02.
3.3.2. 3-Phenyl-2-phenylsufanylbenzo[b]thiophene (5b). A white
solid; mp 125–126 ꢀC (hexane–Et2O). The spectral (IR and 1H NMR)
data for this compound were identical to those reported
previously.4a
3.2.1.6. 4-Methoxyphenyl 2-(4-methylphenyl)sulfanylmethylsulfanyl-
phenyl ketone (2j). A yellow oil; Rf 0.36 (1:2 Et2O–hexane); IR (neat)
1659 cmꢁ1; 1H NMR (500 MHz)
d 2.30(s, 3H), 3.87(s, 3H), 4.22(s, 2H),
6.90 (d, J¼8.7 Hz, 2H), 7.05 (d, J¼8.2 Hz, 2H), 7.24 (d, J¼8.2 Hz, 2H),
7.34–7.46 (m, 3H), 7.61 (d, J¼7.8 Hz, 1H), 7.76 (d, J¼8.7 Hz, 2H). Anal.
Calcd C22H20O2S2: C, 69.44; H, 5.30. Found: C, 69.21; H, 5.37.
3.3.3. 3-(3-Methylphenyl)-2-methylsulfanylbenzo[b]thiophene (5c). A
pale-yellow oil; Rf 0.39 (hexane); IR (neat) 1605,1425 cmꢁ1; 1H NMR
(500 MHz)
d 2.44 (s, 3H), 2.48 (s, 3H), 7.24–7.33 (m, 5H), 7.40 (dd,
J¼7.8, 7.3 Hz, 1H), 7.53 (dd, J¼6.9, 2.3 Hz, 1H), 7.78 (dd, J¼7.3, 1.8 Hz,
1H); MS m/z 270 (Mþ, 100). Anal. Calcd C16H14S2: C, 71.07; H, 5.22.
Found: C, 70.99; H, 5.27.
3.2.1.7. 2-(4-Chlorophenyl)sulfanylmethylsulfanylphenyl 4-methoxy-
phenyl ketone (2k). A yellow oil; Rf 0.28 (1:4 Et2O–hexane); IR (neat)
1653 cmꢁ1 1H NMR (500 MHz)
; d 3.88 (s, 3H), 4.24 (s, 2H), 6.91 (d,
J¼9.2 Hz, 2H), 7.19 (d, J¼8.7 Hz, 2H), 7.24 (d, J¼8.7 Hz, 2H), 7.35–7.46
(m, 3H), 7.59 (d, J¼7.8 Hz, 1H), 7.74 (d, J¼9.2 Hz, 2H). Anal. Calcd
C21H17ClO2S2: C, 62.91; H, 4.27. Found: C, 62.91; H, 4.31.
3.3.4. 3-(3-Methylphenyl)-2-phenylsulfanylbenzo[b]thiophene (5d). A
yellow oil; Rf 0.64 (1:4 Et2O–hexane); IR (neat) 1605, 1477 cmꢁ1; 1H
NMR (500 MHz)
d
2.40 (s, 3H), 7.19 (tt, J¼7.3, 1.4 Hz, 1H), 7.22–7.29
(m, 7H), 7.34–7.38 (m, 3H), 7.60 (dd, J¼7.8,1.8 Hz,1H), 7.77 (dd, J¼7.8,
1.4 Hz, 1H); MS m/z 332 (Mþ, 100). Anal. Calcd C21H16S2: C, 75.86; H,
4.85. Found: C, 75.63; H, 5.02.
3.2.2. 2-Methyl(or phenyl)sulfanylmethylsulfanylphenyl phenyl ke-
tones 2l or 2m. These compounds were prepared by treating
(2-chloro-5-nitrophenyl)phenylmethanone (3) with sodium sulfide
nonahydrate in DMF at room temperature and subsequent
S-methyl(or phenyl)sulfanylmethylation with the respective
chloromethyl sulfides at the same temperature.
3.3.5. 3-(4-Chlorophenyl)-2-methylsulfanylbenzo[b]thiophene (5e). A
yellow oil; Rf 0.23 (hexane); IR (neat) 1424 cmꢁ1; 1H NMR (400 MHz)
d
2.48 (s, 3H), 7.29–7.34 (m, 2H), 7.41 (d, J¼8.7 Hz, 2H), 7.47–7.50 (m,
3H), 7.79 (dd, J¼6.4, 2.4 Hz, 1H); 13C NMR
d 19.90, 121.83, 122.37,
3.2.2.1. 2-Methylsulfanylmethylsulfanyl-5-nitrophenyl phenyl ke-
124.38, 124.67, 128.73, 131.35, 132.97, 133.68, 135.80, 135.90, 139.53,
139.63; MS m/z 290 (Mþ, 100). Anal. Calcd C15H11ClS2: C, 61.95; H,
3.81. Found: C, 61.72; H, 4.02.
tone (2l). A yellow oil; Rf 0.31 (1:3 Et2O–hexane); IR (neat) 1661,
1516, 1344 cmꢁ1; 1H NMR (500 MHz)
d 2.15 (s, 3H), 4.06 (s, 2H), 7.51
(dd, J¼7.8, 7.3 Hz, 2H), 7.66 (t, J¼7.3 Hz, 1H), 7.69 (d, J¼8.7 Hz, 1H),
7.80 (d, J¼7.8 Hz, 2H), 8.26 (d, J¼2.3 Hz, 1H), 8.32 (dd, J¼8.7, 2.3 Hz,
1H). Anal. Calcd for C15H13NO3S2: C, 56.45; H, 4.08; N, 4.38. Found:
C, 56.39; H, 4.16; N, 4.25.
3.3.6. 3-(4-Chlorophenyl)-2-phenylsulfanylbenzo[b]thiophene (5f). A
pale-yellow solid; mp 108–110 ꢀC (hexane); IR (KBr) 1482 cmꢁ1; 1H
NMR (400 MHz)
J¼8.4 Hz, 2H), 7.56 (dd, J¼7.3, 1.8 Hz, 1H), 7.78 (dd, J¼7.3, 1.8 Hz, 1H);
13C NMR
122.12, 123.40, 124.70, 125.40, 126.89, 128.69, 128.93,
d 7.18–7.28 (m, 5H), 7.32–7.40 (m, 4H), 7.44 (d,
3.2.2.2. Phenyl 2-phenylsulfanylmethylsulfanyl-5-nitrophenyl ke-
d
tone (2m). A pale-yellow solid; mp 65–67 ꢀC (hexane–CH2Cl2); IR
129.11, 131.11, 131.37, 132.64, 133.99, 136.63, 139.21, 140.70, 141.23;
MS m/z 352 (Mþ, 100). Anal. Calcd C20H13ClS2: C, 68.07; H, 3.71.
Found: C, 68.08; H, 3.74.
(KBr) 1651, 1504, 1341 cmꢁ1 1H NMR (500 MHz)
; d 4.38 (s, 2H),
7.25–7.28 (m, 3H), 7.38 (dd, J¼7.8, 1.8 Hz, 2H), 7.50 (d, J¼7.8,
7.3 Hz, 2H), 7.64 (t, J¼7.3 Hz, 1H), 7.69 (d, J¼9.2 Hz, 1H), 7.76 (d,
J¼7.8 Hz, 2H), 8.26 (d, J¼2.3 Hz, 1H), 8.30 (dd, J¼8.7, 2.3 Hz, 1H).
Anal. Calcd C20H15NO3S2: C, 62.97; H, 3.96; N, 3.67. Found: C,
62.73; H, 4.12; N, 3.42.
3.3.7. 3-(4-Chlorophenyl)-2-(4-chlorophenyl)sulfanylbenzo[b]-
thiophene (5g). A white solid; mp 100–102 ꢀC (hexane); IR (KBr)
1476 cmꢁ1
;
1H NMR (400 MHz)
d
7.15 (d, J¼8.8 Hz, 2H), 7.21 (d,
J¼8.8 Hz, 2H), 7.34–7.42 (m, 4H), 7.45 (d, J¼8.8 Hz, 2H), 7.57 (d,
3.3. Typical procedure for the preparation of 3-aryl-2-
aryl(or methyl)sulfanylbenzo[b]thiophenes 5
J¼7.8, 1.4 Hz, 1H), 7.79 (d, J¼7.3 Hz, 1H); 13C NMR
d 122.17, 123.54,
124.83, 125.64, 128.76 (2C), 129.24, 129.98, 131.31 (2C), 132.45,
132.91, 134.15, 135.24, 139.12, 141.28; MS m/z 386 (Mþ, 100). Anal.
Calcd C20H12Cl2S2: C, 62.02; H, 3.12. Found: C, 61.83; H, 3.17.
3.3.1. 2-Methylsulfanyl-3-phenylbenzo[b]thiophene (5a). To a stir-
red solution of LDA (1.5 mmol) in DME (3 mL) at ꢁ78 ꢀC, generated
from i-Pr2NH and n-BuLi by the standard method, was added a so-
lution of 2a (0.20 g, 0.73 mmol) in DME (2 mL) dropwise; the
mixture was stirred for 1 h at the same temperature. Saturated
aqueous NH4Cl (10 mL) was added, and the organic materials were
extracted with Et2O twice (10 mL each). The combined extracts
were washed with brine, dried over anhydrous Na2SO4, and con-
centrated by evaporation to give the crude 2-methylsulfanyl-3-
phenyl-2,3-dihydrobenzo[b]thiophene-3-ol (4a). This was used in
the next dehydration reaction without any purification. Thus, the
3.3.8. 3-(4-Methoxyphenyl)-2-methylsulfanylbenzo[b]thiophene (5h).
A
white solid; mp 84–85 ꢀC (hexane–Et2O); IR (KBr) 1611,
1526 cmꢁ1 1H NMR (400 MHz)
; d 2.47 (s, 3H), 3.88 (s, 3H), 7.04 (d,
J¼8.8 Hz, 2H), 7.29–7.31 (m, 2H), 7.40 (d, J¼8.8 Hz, 2H), 7.53 (dd,
J¼6.6, 2.6 Hz, 1H), 7.77 (dd, J¼7.3, 1.8 Hz, 1H); MS m/z 286 (Mþ, 100).
Anal. Calcd C16H14OS2: C, 67.10; H, 4.90. Found: C, 66.94; H, 5.16.
3.3.9. 3-(4-Methoxyphenyl)-2-phenylsulfanylbenzo[b]thiophene (5i).
A pale-yellow solid; mp 106–107 ꢀC (hexane–Et2O); IR (KBr) 1611,